In modern internal combustion engines, devices for variably adjusting the timing of gas exchange valves, also referred to as camshaft adjusters, are used in order to be able to vary the phase position of a camshaft relative to a crankshaft in a defined angle range between a maximum advanced position and a maximum retarded position. The cams of the camshaft normally bear against cam followers, for example bucket tappets, rocker arms or oscillating arms. When a camshaft is set in rotation, the cams roll on the cam followers, which in turn actuate the gas exchange valves. Both the opening duration and also the amplitude, and also the opening and closing times of the gas exchange valves, are thus defined by the position and the shape of the cams.
The angular displacement of the camshaft in relation to the crankshaft in order to obtain optimum timing for different engine speed and load states is referred to as camshaft adjustment. One design variant of a camshaft adjuster operates for example on the basis of the so-called oscillating motor principle. Here, a stator and a rotor are provided which are arranged coaxially and which are movable relative to one another. The stator and the rotor together form a hydraulic chamber pair. Here, a chamber pair is delimited in each case by webs of the stator and is divided by a respective vane of the rotor into two oppositely-acting pressure chambers, the volumes of which are varied in opposition to one another by means of a relative rotational movement of the rotor with respect to the stator. In the position of maximum adjustment, the respective vane bears against one of the edge-side webs of the stator. The relative rotational movement of the rotor is realized by means of an adjustment of the vane by virtue of a hydraulic medium or pressure medium, such as for example oil, being introduced via pressure medium ducts into one of the pressure chambers of the chamber pairs and pushing the vane away. The pressure medium ducts open out on both sides of the respective vane, such that the hydraulic medium is conducted into the respective pressure chamber. With the adjustment of the rotor, the camshaft which is fastened to the rotor is adjusted for example in the advanced direction, that is to say of an earlier opening time of the gas exchange valves. With an adjustment of the rotor in the opposite direction, the camshaft is adjusted relative to the crankshaft in the retarded direction, that is to say toward a later opening time of the gas exchange valves.
An undesired exchange of oil between the pressure chambers of a chamber pair may take place in the region of contact between the vane of the rotor and an inner lateral surface of the stator, because the sealing length of the vane in the circumferential direction is relatively small. To prevent leakage at this location, the camshaft adjuster from DE 10 2006 004 718 A1 comprises a U-shaped sealing element comprised of a spring steel or a resiliently elastic plastic. The sealing element has a base limb, which is oriented substantially in the circumferential direction, and two radially oriented side limbs, which engage over the vane. An outer side of the base limb is of substantially concave form, such that the base limb has two maxima in the region of the side limbs and has an approximately central minimum. The base limb bears against the lateral surface of the stator in the region of its maxima. In the region of the minimum, the sealing element bears against a radial surface of the vane.
For failure-free operation of the camshaft adjuster, it is furthermore highly important not only to minimize leakage between the oppositely acting pressure chambers but rather also to prevent the oil from flowing out of the pressure chambers and back into the pressure medium ducts.